The present invention relates to removing excess heat from electronic circuit housings and, more particularly, to the removal of such heat through use of heat transporting coolants.
The operation of electronic circuits inevitably involves the dissipation of electrical energy into heat in the electronic and passive circuit device structures used in forming such circuits. These circuits are typically provided for use by being housed in some kind of housing arrangement. In those situations in which the generated heat is sufficiently removed simply through convection or conduction to the surrounding atmosphere, or both, to thereby avoid raising temperatures to values that could lead to failures in the circuits or the housings in which they are positioned, nothing more is needed for cooling such circuit housing arrangements.
However, some kinds of electronic circuits are used to control relatively large amounts of electrical power and are often provided in large power dissipation electronic module assemblies. Correspondingly, such circuits dissipate relatively large amounts of electrical power in the controlling of these much larger amounts of electrical power, and so result in the generation of too much heat in the housing arrangements for removal by just atmospheric based convection and conduction means. In these situations, further housing cooling provisions must be made to avoid temperatures in those housings being raised to values that lead to failures in the circuits or their housings. A typical such further provision is a duct, in which a coolant can be caused to flow to form a heat exchanger, and this duct is thermally coupled to one side of the electronic circuit housing being cooled thereby.
Such a duct provision for circuit housings, while an improvement over relying on just atmospheric based conduction and convection, is only a limited improvement for circuit housings in which the supported circuits generate sufficiently large amounts of heat primarily because of the thermal resistivity encountered over the transport paths. That is, although the cooling duct removes heat well from the circuit and housing portions relatively close thereto, heat that must be transported thereto from more remote portions thereof, usually mostly by conduction, is limited often by the relatively small thermal conductivities of the materials present along those transport paths. Those thermal conductivities can be improved by use of alternative materials along the transport paths or by adding more parallel paths through broadening the heat sources such as by using heat generating components having larger sizes or lateral extents, or by enlarging the housing to have more area abutting the cooling duct. Such remedies, however, either substantially add to the cost or the weight of the circuit housings, or both. Thus, there is a desire for better arrangements to sufficiently remove excessive heat generated in housed circuit devices during their operation.